大采高工作面采场围岩结构力学分析及其工程应用

Mechanical analysis and engineering application of surrounding rock in large mining height working face

综合考虑顶底板岩层破断以及硬岩层与软岩层的耦合作用,构建采场围岩“椭圆应力拱”结构力学模型,研究“椭圆应力拱”周边切向应力与轴长、轴比、极角等参数之间的关系,分析“椭圆应力拱”、悬臂梁、铰接岩梁三者之间相互作用机制。研究认为:“椭圆应力拱”承载了采场围岩大部分载荷,前、后拱脚随工作面开采向前移动;采场围岩重新分布应力,在拱顶和拱底附近区域,形成拉应力,使岩层产生“主动破断”,并挤压其运动方向上的岩层;在远离拱顶和拱底区域,形成压应力,夹持尚未破断的岩层。在岩层自重载荷、“主动破断”岩层的挤压载荷,以及应力拱周边压应力的夹持作用下,岩层沿拱迹线“被动破断”;“椭圆应力拱”内尚未破断的硬岩层形成“悬臂梁”,硬岩层破断后形成“铰接岩梁”,软岩层破断后以载荷的形式作用于其下部的岩层上,工作面支架和煤壁承受了顶、底板“悬臂梁”或“铰接岩梁”传递来的岩层载荷,“悬臂梁”的被动破断及“铰接岩梁”失稳直接影响到工作面支架及煤壁的稳定性。基于此,编程计算工作面开采过程中“椭圆应力拱”的轴长、圆心坐标、拱脚位置等位置参数,确定大采高工作面顶、底板岩层裂隙发育深度,为大采高工作面防突水提供一些理论参考。

Considering the fracture of roof and floor rock and the coupling effect of hard rock and soft rock,the structural mechanical model of“elliptic stress arch”of surrounding rock was constructed,the relationship between the tangential stress on boundary of the“elliptic stress arch”and parameters such as axial length,axial ratio and polar angle was studied,and the interaction mechanism among“elliptic stress arch”,cantilever beam and articulated rock beam was analyzed.The research shows that“elliptic stress arch”carries most of the load from the surrounding rock,the front and back arch feet move forward with working face mining;the stress is redistributed in the surrounding rock,forming tensile stress near the arch crown and arch bottom and resulting in“initiative breaking”of the rock stratum which squeezes the rock stratum in its movement direction;in the area far from the arch crown and arch bottom,compressive stress is formed to clamp the rock stratum that has not been broken.Under the clamping behavior from the self-weight load of the rock stratum,the pressing load of“initiative breaking”rock stratum and compressive stress around the stress arch,the rock stratum“passive breakage”along the arch trace;the unbroken hard rock strata in the“elliptic stress arch”forms a“cantilever beam”,and the hard rock strata forms a“articulated rock beam”after breaking.Meanwhile,the soft rock strata act on the rock strata below it in the form of load after breaking,the working face supports and coal wall bear the rock strata load transmitted by the“cantilever beam”or“articulated rock beam”from the roof and floor.Based on the passive breaking of“cantilever beam”and the instability of“articulated rock beam”directly affect the stability of working face support and coal wall,the position parameters such as the axis length,center coordinates and arch foot position of the“elliptic stress arch”in the mining process of the working face are programmed to determine the development depth of rock fissures in the roof and floor of the large mining height working face,so as to provide some theoretical references for water inrush prevention in the large mining height working face.